euphemism vs underplaying

euphemism

noun
  • The use of a word or phrase to replace another with one that is considered less offensive, blunt or vulgar than the word or phrase which it replaces. 

  • A word or phrase that is used to replace another in this way. 

underplaying

How often have the words euphemism and underplaying occurred in a corpus of books? (source: Google Ngram Viewer )